1. Field of the Invention
This invention relates in general to certain new and useful improvements in wheelchairs, and more particularly, to improved and foldable wheelchairs which can be constructed in a variety of sizes from standard sized components and which also have front and back wheels adjustably positionable thereon, and which can be used in normal riding conditions and in sports activities.
2. Brief Description of the Prior Art
Wheelchair constructions have remained unchanged, except for relatively minor features, for a substantial period of time. While wheelchairs have existed for many years, they generally were constructed of a main frame, front and rear wheels, side rails or so-called "arm rests" and foot support members. However, there was no means for creating or manufacturing wheelchairs of different sizes, at a relatively low cost, from standard sized components, in order to accommodate different size users, or users with various forms of disabilities. While the prior art has disclosed foldable wheel chairs, the prior art has not provided a wheelchair which is foldable and which also has all of the advantages of manufacturing wheelchairs of different sizes from commonly sized components and which can be used in normal riding conditions and in sports activities.
Prior art wheelchair manufacturers constructed several different sized wheelchairs and used different size components for each of the differently sized wheelchairs. In the case of a tall individual, the main frame had to be larger, the seat located in a different position, and a foot support member extended further from the seat, than in the case of a wheelchair for a smaller individual. In addition, for the larger sized wheelchair, the seat may have to be located at a higher elevation in order to permit the user to engage rims on the wheels for propelling the wheelchair in an easy and convenient manner.
Notwithstanding, heretofore there has not been any foldable and operable wheelchair which was designed for normal transport and for sports activities and which was durable and presented a high degree of stability. In other words, such wheelchairs heretofore constructed were not designed to permit any form of athletic activity, and particularly, for fast-moving sports activities and which are stable and durable. This was primarily due to the fact that the prior art wheelchairs were all of a box-like construction with the seat, and hence, the center of gravity, located at a fixed and at a substantial distance above the ground. Consequently, the prior art wheelchairs were not designed for any fast movement, and if one attempted to propel any of the prior art wheelchairs and particularly foldable and expandable wheelchairs, at any significant speed, or attempted to turn a corner quickly, the wheelchair might well tip over, resulting in injury to the user.
In recent years, it has been found to be highly beneficial for paraplegics and others required to use wheelchairs on a relatively permanent basis to engage in various forms of athletic activities, including wheelchair racing, tennis, and the like. However, the wheelchair constructions heretofore did not lend themseleves to such forms of activities. More specifically, it was found to be necessary to provide wheelchairs of this type which are collapsable and foldable and also openable for use.
For the more seriously handicapped people, particularly with high level back injuries which limited the mobility of the handicapped users arms, the conventional wheelchairs are difficult to use. This is due to the heavy construction and resultant weight of the conventional wheelchairs, which make it more difficult for the injured party to use and to manuever. As a result, people with such injuries had to resort to the use of motor powered wheelchairs, as for example, electric motor powered wheelchairs which use a battery source of power. These motor powered wheelchairs are quite expensive and require periodic maintenance, which thereby militates against widespread use. Further, these wheelchairs require frequent recharging, when battery powered.
U.S. Pat. No. 3,937,490 to Nasr discloses a wheelchair having some degree of adjustability to suit several body sizes and deformities. Particularly, the width of the seat and back rest panels may be adjusted, and the length of the seat may be adjusted. However, this patent does not disclose a wheelchair which can be made from a common main frame and a variety of commonly sized components which are capable of being mounted in a desired location in the same manner as taught and claimed in the instant application. U.S. Pat. No. 4,046,374 to Breyley discloses a walking aid which includes caster wheels. In addition, the walking aid is provided with telescopically located adjustable members.
U.S. Pat. No. 2,847,058 to R. E. Lee discloses a folding wheelchair which includes cross-bars extending between frame sections. However, the wheelchair uses a complex construction and the means for folding the wheelchair and moving it into an expanded and opened position for use is not sufficient to create a desire degree of stability, particularly in sports activities.
U.S. Pat. No. 3,331,614 to J. L. McClintock also discloses a foldable wheelchair using cross-lever arms. Hereagain, the single pair of cross-lever arms connecting the two opposed frame sections does not provide the necessary rigidity even in normal use conditions, let alone sports activities.
U.S. Pat. No. 2,181,420 to Everest et al discloses one of the basic forms of foldable wheelchairs. This particular wheelchair also utilizes a pair of cross-lever arms for connecting two opposed wheel frame sections. Consequently, it suffers from the same disadvantages in that stability and rigidity are not obtainable with this type of construction.
U.S. Pat. No. 4,166,631 dated Sept. 4, 1979 to David Sanaski also discloses a foldable wheelchair which can be used in sports activities. This wheelchair also features a pair of cross-lever arms connecting a seat structure to a pair of opposed frame sections. However, this wheelchair suffers from many disadvantages including the primary fact that it is really not very stable in normal transport and even less stable in sports activities. Specifically, the single pair of cross-lever arms connecting the opposed frame sections and the seat structure is not sufficient to maintain the desired rigidity even in normal transport when being used by an occupant of the wheelchair.
The wheelchair of the Sanaski Patent requires four points of connection of the main frame to the seat structure in order to achieve at least some desired rigidity. In other words, the frame of the buttocks supporting portion of the seat structure is necessarily connected to the pair of opposed frames on at least four quadralaterally located points. Notwithstanding, even this construction is not sufficient to provide the necessary rigidity. In fact, the Sanaski Patent specifically points out that the "sway bar" effect is desired. While this may be effective on some occasions, it is not effective in sports activities. In addition, due to the fact there is this flexibility in the construction, the wheelchair is not very responsive to quick turns or manuevability. Moreover, it does not provide the desired support and stability which would be desired by users in normal operation.
U.S. Pat. No. 2,561,616 to Everest et al and U.S. Pat. No. 2,486,015 to Everest et al also disclose collapsable or so-called "foldable" wheelchairs similar to that in the Sanaski Patent. The wheelchairs in each of these Everest et al Patents also employ only a single pair of cross-over arms or links and therefore suffer from the same disadvantages as does the wheelchair taught in the Sanaski Patent.